About half a million people selected a health insurance plan in the first week of the 2015 enrollment period under the Affordable Care Act, according to a new federal report that underscores huge progress since last year, when website problems made signing up for coverage nearly impossible.

From Nov. 15 to Nov. 21, the Department of Health and Human Services announced, 462,125 people signed up for a plan through HealthCare.gov, the federally run insurance marketplace that serves 37 states nationwide.

Tens of thousands of additional people signed up for coverage on state-run marketplaces in the remaining 13 states, including California, Maryland and Connecticut, and the District of Columbia. California reported last week that more than 11,000 people had selected plans in the first four days of open enrollment.

The HealthCare.gov total — which is split roughly evenly between new enrollees and people renewing coverage they had in 2014 — is a major advance from last year, when the website did not work for more than a month.

Just 106,000 people signed up for coverage in the first month of open enrollment last year.

This year, it appears that the site is working far better. Administration officials said Wednesday it had not crashed since it opened, though it had twice directed users to an online “waiting room” that is deployed when there is high volume or other technical issues with the site.

In total, more than 3.7 million users visited HealthCare.gov in the first week of the new enrollment period, according to the health agency.

And in another indication of improvement, wait times at call centers around the country averaged only a little more than three minutes.

Still, it remains unclear whether the Obama administration will be able to hit enrollment targets by the time the sign-up period closes in 2 1/2 months.

The tally released Wednesday counts only plan selections, not the number of people who have paid premiums, which is usually lower. Consumers have until the middle of December to pay in order to guarantee they have coverage starting Jan. 1.

“We had a solid start, but we have a lot of work to do every day between now and Feb. 15,” Health and Human Services Secretary Sylvia Mathews Burwell said in a statement, referring to the date that open enrollment ends.

The law allows Americans who don’t get health benefits at work to shop among plans on new state-based marketplaces.

Consumers making less than four times the federal poverty level — or about $94,000 for a family of four — qualify for subsidies.

This year, consumers who already have coverage through the marketplace have until Dec. 15 to go back and shop for plans before they are automatically re-enrolled in their current plan. Administration officials are strongly urging these people to shop, as they will probably be able to find lower-priced options.

Total enrollment in the marketplaces, although an imprecise metric, has been watched closely because sustained growth is considered vital to reducing the number of uninsured and keeping premiums in check by getting healthier Americans into the market.

The Department of Health and Human Services, which had initially predicted 13 million customers in the second year of the marketplaces, now says 9 million to 9.9 million people probably will get coverage by the end of next year. About 6.7 million people had health plans through the marketplaces before the open enrollment period began Nov. 15, according to the federal agency.

Administration officials last week downgraded the tally from 7.1 million after it was discovered the figure included about 400,000 people who had only dental plans.

Surveys suggest that about 8 million to 10 million uninsured people have gained coverage this year since the marketplaces opened and Medicaid was expanded in many states under the law. About 30 million people remain uninsured, however.